Until now, campaigners have failed to establish a causal link between the drug prescribed by GPs during the Sixties and Seventies and the birth defects. But the discovery of thousands of pages of previously unseen documents has given them new hope of justice.

The papers, which were unearthed in the Berlin National Archives, will be examined by a committee of experts.

Labour MP Yasmin Qureshi believes 'there may have been a cover-up'Credit:
AP

Yasmin Qureshi, the Labour MP, who has long supported the families in their battle for justice, told The Telegraph: “These documents form a significant discovery and could lead to important developments.

“I believe there may have been a cover-up over the effect of this drug on pregnant mothers.”

Marie Lyon, whose daughter Sarah was born with a foreshortened arm and believes that the tablets stunted her development in the womb, welcomed the discovery. She said: “It’s unthinkable that more than 40 years after our children were born, neither the sufferers nor their mothers have had justice.”

The files, which had been stored in archives for decades, showed that in January 1975, Dr William Inman, principal medical officer for the British Government, had found that women who took a hormone pregnancy test “had a five-to-one risk of giving birth to a child with malformations”.

Dr Inman wrote to Primodos’s German manufacturer, Schering, so the firm could “take measures to avoid medico-legal problems”, rather than recall the drug. A later document explains that Dr Inman destroyed the materials on which his findings were based, “to prevent individual claims being based on his material”.

The Berlin archive documents will be examined by the Commission on Human Medicines’ Expert Working Group on Hormone Pregnancy Tests.

It is now known that one dose of Primodos contained super-strength hormones that, later, would be used in the morning-after pill.

In 1967 a paediatrician called Isabel Gal found that a high proportion of babies born with spina bifida had mothers who had taken hormonal pregnancy tests. She fought a 10-year battle to get the drug removed from the market, but said she was stonewalled at every turn.

Marie Lyon, whose daughter Sarah was born with a foreshortened arm, is chair of the Association for Children Damaged by Hormone Pregnancy TestsCredit:
PAUL COOPER

A Sky Atlantic documentary to be broadcast on Tuesday discloses that a separate document showed a warning had been placed on Primodos packets by UK regulators in June 1975.

It stated that the drug should not be taken during pregnancy because of the risk that it may cause malformations. These documents were found by Karl Murphy, 44, who was born with shrivelled hands and feet and whose mother, Pam, had been part of a campaign group that attempted to prove Primodos had harmed their babies.

Despite the evidence accumulated over the years, an attempt to bring the case to court by the alleged victims in 1982 collapsed and legal aid was withdrawn from the 700 families who were suing the drug’s manufacturer, Schering, for compensation.

It was deemed unlikely that they would be able to prove a causal link between the drug and the malformations suffered by their children.

Schering is now owned by Bayer, which insists that sales of Primodos in were “in compliance with prevailing laws”. The pharmaceutical giant said that the view – both at the time and, after a full review, today – is that “evidence for a causal association between the use of hormonal pregnancy tests and an increased incidence of congenital malformations was extremely weak”.

Bayer “rejects any suggestion” that anything has been concealed by Schering, other than privileged documents.